The invention relations in general to structural engineering and, in particular, to a modular approach to designing structural components. In designing a structural unit, e.g., the frame of a vehicle, each constituent member or component of the structural unit typically is designed in its entirety specifically for the structural loads (tensile, compressive, and/or shear forces, torques, and/or bending moments) to which it will be subjected. Such an approach to designing and building a structural assembly such as an automotive frame increases the time and cost both to design and build the assembly.